This invention relates to a printing system comprising such components as a computer terminal and printer connected by a network, by way of example.
When printer information is monitored from a host computer via a network, the conventional approach is to adopt a polling method in which the host computer (referred to as the xe2x80x9chostxe2x80x9d below) periodically sends the monitored printer a command for obtaining the status of the printer and receives a response from the printer. Using polling makes it possible for the host to acquire the status of the printer at any desired timing. However, if there are many hosts on the network and these hosts monitor the status of a single printer, polling results in a very large number of packets being sent on the network in order to acquire the printer status. This not only increases the load on the network controller of the printer but also increases the load on the entire network. There is the danger, therefore, than this will cause the network to go down.
Rather than monitoring printer status by such polling, a method being considered involves the printer notifying the host of its status when the printer status changes. If the host monitors printer status using this method, it is possible to reduce the load on the network controller of the printer and the load on the network, thus enabling monitoring to be performed more efficiently.
In this method of monitoring printer status based upon notification from the printer, it is required that the host that is the destination of the status report from the printer be registered with the printer. The printer notifies the registered host of its changed status. This means that if the host wishes to monitor the status of the printer, it is required that the host be registered with the printer as the destination of the report of the change in status. If it then becomes unnecessary for the host to monitor the status of the printer, it is required that the host be deleted from report destinations registered with the printer.
In this method, the report destinations are controlled not by the printer but by the host. The registered report destinations are never deleted under the control of the printer without an instruction from the host. Therefore, a problem arise in that if the host goes down and cannot be deleted from the status-change report destinations registered in the printer, the printer will continue to notify the host of changes in its status.
Since a report destination that has failed to be deleted will not be deleted as long as the printer power supply is not turned off, the memory area that is for registering report destinations becomes cluttered and it will eventually become impossible for the printer to register a notification request from any host.
Accordingly, an object of the present invention is to provide a printing apparatus, printing system and method of controlling the same in which the destination of a status-change report can be updated automatically by providing registration of a status-change report with an expiration time.
According to the present invention, the foregoing object is attained by providing a printing system comprising a computer terminal and a network printer, wherein the computer terminal includes: means for creating a status notification request which causes printer status to be posted periodically; means for periodically transmitting a printer-status notification registration request; means for transmitting a printer-status notification deletion request; means for receiving printer status notification from the printer; and means for displaying printer status in dependence upon the printer status; and the network printer includes: means for receiving a printer-status notification registration request from at least one computer; means for registering each printer-status notification registration request as registration information; means for deleting the registration information if the printer-status notification registration request has not been received from the same computer within a registration retention time defined in the printer-status notification registration request; means for updating the registration retention time anew if the printer-status notification registration request has been received from the same computer within the registration retention time defined in the printer-status notification registration request; sensing means for sensing a change in printer status; means for notifying a network address of a computer, which is defined in the registration information, of a change in printer status sensed by the sensing means; means for receiving the printer-status notification deletion request of a computer; and means for deleting the registration information in response to the printer-status notification deletion request.
Further, the foregoing object is attained by providing a printing apparatus for accepting a status notification request from an external device, registering the device as a destination of status notification and notifying the registered device of a change in status, wherein after status notification is requested by a certain device, this device is removed as a destination of status notification if a status notification request is not made by the device afresh upon elapse of a predetermined period of time.
Further, the foregoing object is attained by providing a printing system having at least one information processing apparatus and a printing apparatus, wherein the information processing apparatus issues a status notification request to the printing apparatus at prescribed time intervals, and the printing apparatus registers the information processing apparatus that issued the status notification request as a destination of status notification, and invalidates this registration if, after the registration is made, a predetermined period of time elapses without receipt of a status notification request afresh.
Further, the foregoing object is attained by providing a method of controlling a printing system, in which a status notification request is issued from an information processing apparatus to a printing apparatus, and whenever the status notification request is received, the printing apparatus registers, as a destination of status notification, the information processing apparatus that issued the status notification request, and invalidates this registration if, after the registration is made, a predetermined period of time elapses without receipt of a status notification request afresh.
Further, the foregoing object is attained by providing a computer-readable storage medium storing a program that causes a computer to execute the following functions: accepting a status notification request from an external device registering the device as a destination of status notification; notifying the registered device of a change in status; and after status notification is requested by a certain device, removing this device as a destination of status notification if a status notification request is not made by the device afresh upon elapse of a predetermined period of time.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.